Height of chairs is a continuing problem for me. I'm not hugely tall (about 6'2"), but virtually all folding chairs are too short for me to be comfortable in them, and much to short for tuba playing. With my tuba seat-stand, it gives me enough height (in addition to the tuba support), that I'm generally okay. Even so, there are some chairs that are just too small. I have my own (Walmart), but it's not really tall enough either. I've looked into buying a folding chair that is taller, but they seem to be pretty pricey. So I feel your pain. However, I'm not prepared to lug around a drum throne (which I've also considered). At the moment, I've got things so that I have just my tuba and my large junk bag (which holds even my seat stand). On some occasions I need to take a stand, but with the tuba on my back, I can still do everything in one trip.
About a year ago on Tubnet, the question of lugging was discussed, and one thing that came up was this: http://www.discountramps.com/folding-beach-chair/p/BFC/. I'm still thinking of getting one of these -- not for the tuba and equipment but as a cart for hauling surf fishing stuff. Note that it has several advantages over other alternatives: (1) It's not expensive, (2) it's light (aluminum tube construction), (3) it FOLDS pretty compactly, and (3) it has large pneumatic tires (essential for going across any uneven/muddy/gravel/sandy ground). Also, you can sit in it (though it's definitely too low for a tuba chair.
I'm afraid the next step up would be to trailer a 4-wheeler to sites and use it to transport instruments and assorted accessories. I've got the trailer, but I'm reluctant to acquire another motorized vehicle just to play a gig.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)